Intracellular bacteria of the genus Chlamydia are among the most common human pathogens and are the leading bacterial cause of sexually transmitted disease and preventable blindness. See Schachter, J. (1999) in Chlamydia, ed. Stephens, R. S. (Am. Soc. Microbiol., Washington, D.C.), pp. 139–169. Over the last decade, Chlamydia pneumoniae has been identified in a high proportion of atherosclerotic lesions, suggesting a role for chlamydial infection in coronary heart disease. See Saikku et al. (1988) Lancet ii: 983–986; Jackson et al. (1997) Am J. Pathol. 150: 1785–1790. Recently, Chlamydia has been detected in brain lesions of patients with Alzheimer's disease. See Balin et al. (1998) Med. Microbiol. Immunol. 187: 23–42.
In early trials, vaccination against Chlamydia trachomatis surprisingly increased rate and severity of the naturally acquired chlamydial eye disease, trachoma, whereas in other trials the rate of disease declined but the severity increased. See Ward, M. E. (1999) in Chlamydia, ed. Stephens, R. S. (Am. Soc. Microbiol., Washington, D.C.) pp. 171–210. The high seroprevalence of C. pneumoniae infection is not accompanied by equally high organism isolation or disease rates. See Saikku, P. (1998) in Chlamydial Infections: Proceedings of the Ninth International Symposium on Human Chlamydial Infection, Napa, Calif., June 1998, ed. Stephens, R. S. (Univ. of California Press, Berkeley), pp. 145–154. Collectively, these data support the notion that some individuals react with increased sensitivity to repeated exposure to chlamydial agents whereas others develop a protective response. Similarly, animal studies indicate that genetic determinants of the host response to Chlamydia spp. play a decisive role in the outcome of chlamydial infection. See Yang et al. (1996) J. Immunol. 156: 4338–4344.
Thus, there is a need to identify and study causes of unfavorable reactions to chlamydial infection. Accordingly, there is a need for non-human disease models which are suitable for evaluating the effects of therapeutic and prophylactic treatments on chlamydial infection.